U.S. patent application number 13/207526 was filed with the patent office on 2012-12-27 for power system driven by a low-temperature heat source.
Invention is credited to Ming-Hui Ho, Uzu-Kuei Hsu, Jr-Ming Miao, Chang-Hsien Tai.
Application Number | 20120324892 13/207526 |
Document ID | / |
Family ID | 47360511 |
Filed Date | 2012-12-27 |
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United States Patent
Application |
20120324892 |
Kind Code |
A1 |
Tai; Chang-Hsien ; et
al. |
December 27, 2012 |
Power System Driven By A Low-Temperature Heat Source
Abstract
A power system driven by a low-temperature heat source includes
a power cycling unit and a heat pump unit. The power cycling unit
includes a turbine, a condenser, a pump, a first heat exchanger,
and a second heat exchanger. The turbine, the condenser, the pump,
the first heat exchanger, and the second heat exchanger are
connected in sequence. The heat pump unit includes a condenser and
an evaporator. The condenser of the heat pump unit is connected to
the second heat exchanger. The evaporator is connected to the
condenser of the heat pump unit. The evaporator absorbs heat of a
working fluid in a waste heat pipe.
Inventors: |
Tai; Chang-Hsien; (Pingtung
County, TW) ; Miao; Jr-Ming; (Pingtung County,
TW) ; Hsu; Uzu-Kuei; (Pingtung County, TW) ;
Ho; Ming-Hui; (Pingtung County, TW) |
Family ID: |
47360511 |
Appl. No.: |
13/207526 |
Filed: |
August 11, 2011 |
Current U.S.
Class: |
60/670 |
Current CPC
Class: |
F01K 3/185 20130101 |
Class at
Publication: |
60/670 |
International
Class: |
F01K 23/06 20060101
F01K023/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 22, 2011 |
TW |
100121890 |
Claims
1. A power system driven by a low-temperature heat source
comprising: a power cycling unit including a turbine, a condenser,
a pump, a first heat exchanger, and a second heat exchanger, with
the turbine, the condenser, the pump, the first heat exchanger, and
the second heat exchanger connected in sequence; and a heat pump
unit including a condenser and an evaporator, with the condenser of
the heat pump unit connected to the second heat exchanger, with the
evaporator connected to the condenser of the heat pump unit, with
the evaporator adapted to absorb heat of a working fluid in a waste
heat pipe.
2. The power system driven by a low-temperature heat source as
claimed in claim 1, with the heat pump unit including a compressor
and a throttle valve, with the compressor, the evaporator, the
throttle valve, and the condenser connected to each other, with the
compressor connected to the turbine of the power cycling unit.
3. The power system driven by a low-temperature heat source as
claimed in claim 1, further comprising: a third heat exchanger
mounted between the second heat exchanger and the turbine, with the
third heat exchanger connected to an auxiliary heat pump unit.
4. The power system driven by a low-temperature heat source as
claimed in claim 3, with the auxiliary heat pump unit including a
compressor connected to the turbine of the power cycling unit.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a power system and, more
particularly, to a power system driven by a low-temperature heat
source.
[0003] 2. Description of the Related Art
[0004] In petrochemical or steel industries, low-temperature heat
sources can be obtained from working fluids at 80-90.degree. C. in
waste heat pipes through use of heat regenerators that recycle heat
energy during processes. The energy can be saved if the
low-temperature heat sources are recycled.
[0005] As an example, FIG. 1 shows a conventional power system 9
including a pump 91, a boiler 92, a turbine 93, and a condenser 94
that are connected to each other by pipes filled with a working
fluid, forming a closed circulating piping system. The pump 91
compresses the working fluid to increase the pressure and
temperature of the working fluid entering the boiler 92. Heat
Q.sub.in is inputted to the boiler 92 by burning natural gas or
kerosene to heat the temperature increased working fluid into steam
through phase change. The steam drives the turbine 93 to output
work W.sub.out.
[0006] However, although the low-temperature heat source is used as
a portion of the heat source for the conventional power system 9,
the heating effect provided by the low-temperature heat source is
limited. As a whole, the work W.sub.out. outputted by the turbine
93 can not reach the ideal value, because the low-temperature heat
source generated during the processes is directly introduced into
the conventional power system 9 through single-stage heat exchange.
As a result, the heat efficiency of the conventional power system 9
is reduced. Thus, improvement to the conventional power system 9 is
required.
SUMMARY OF THE INVENTION
[0007] An objective of the present invention is to provide a power
system driven by a low-temperature heat source. The temperature of
the low-temperature heat source is increased to an ideal value and
then introduced into the power system to increase the effect of the
power system and to fully utilize a large amount of low-temperature
heat source with low enthalpy.
[0008] The present invention fulfills the above objective by
providing a power system driven by a low-temperature heat source
including a power cycling unit and a heat pump unit. The power
cycling unit includes a turbine, a condenser, a pump, a first heat
exchanger, and a second heat exchanger. The turbine, the condenser,
the pump, the first heat exchanger, and the second heat exchanger
are connected in sequence. The heat pump unit includes a condenser
and an evaporator. The condenser of the heat pump unit is connected
to the second heat exchanger. The evaporator is connected to the
condenser of the heat pump unit. The evaporator is adapted to
absorb heat of a working fluid in a waste heat pipe.
[0009] Preferably, the heat pump unit includes a compressor and a
throttle valve. The compressor, the evaporator, the throttle valve,
and the condenser are connected to each other. The compressor is
connected to the turbine of the power cycling unit. By such an
arrangement, the shaft work outputted by the turbine drives the
heat pump unit to save the energy consumed by the compressor.
[0010] The present invention will become clearer in light of the
following detailed description of illustrative embodiments of this
invention described in connection with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The illustrative embodiments may best be described by
reference to the accompanying drawings where:
[0012] FIG. 1 shows a schematic diagram of a conventional power
system.
[0013] FIG. 2 shows a schematic diagram of a power system driven by
a low-temperature heat source of a first embodiment according to
the present invention.
[0014] FIG. 3 shows a temperature-entropy diagram of a power
cycling unit of the first embodiment.
[0015] FIG. 4 shows a schematic diagram of a power system driven by
a low-temperature heat source of a second embodiment according to
the present invention.
[0016] FIG. 5 shows a temperature-entropy diagram of a power
cycling unit of the second embodiment.
[0017] All figures are drawn for ease of explanation of the basic
teachings of the present invention only; the extensions of the
figures with respect to number, position, relationship, and
dimensions of the parts to form the preferred embodiments will be
explained or will be within the skill of the art after the
following teachings of the present invention have been read and
understood. Further, the exact dimensions and dimensional
proportions to conform to specific force, weight, strength, and
similar requirements will likewise be within the skill of the art
after the following teachings of the present invention have been
read and understood.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The term "low-temperature heat source" referred to
hereinafter means a working fluid having a temperature below
100.degree. C. after absorbing industrial waste heat.
[0019] With reference to FIG. 2, a power system driven by a
low-temperature heat source of a first embodiment according to the
present invention includes a power cycling unit 1 and a heat pump
unit 2 connected to the power cycling unit 1.
[0020] The power cycling unit 1 can output shaft work for an
intended use as well as the power for the heat pump unit 2.
Specifically, the power cycling unit 1 includes a turbine 11, a
condenser 12, a pump 13, a first heat exchanger 14, and a second
heat exchanger 15 that are connected in sequence by pipes receiving
a first working fluid. Namely, the first working fluid flows
through the turbine 11, the condenser 12, the pump 13, and the
first and second heat exchangers 14 and 15 and then flows back to
the turbine 11. The turbine 11 can output shaft work W.sub.out and
can drive the heat pump unit 2 to operate. The condenser 12
releases heat from the first working fluid at a constant pressure,
converting the first working fluid from a gas state into a
saturated liquid state. The pump 13 compresses the first working
fluid to increase the temperature and pressure of the first working
fluid. The first heat exchanger 14 absorbs heat Q1 from a working
fluid in a waste heat pipe 8 to preheat the first working fluid of
the power cycling unit 1. The second heat exchanger 15 absorbs heat
Q2' released by the heat pump unit 2, increasing the temperature of
the first working fluid of the power cycling unit 1 to an ideal
value. The heat pump unit 2 is connected to the second heat
exchanger 15 of the power cycling unit 1 to absorb the heat Q2 from
the working fluid in the waste heat pipe 8 and to release the heat
Q2' to the second heat exchanger 15. When the working fluid flows
through an area covered by the first heat exchanger 14, the
temperature of the working fluid drops due to absorption of the
heat Q1 from the working fluid by the first heat exchanger 14.
Thus, it is not easy to recycle and reuse the working fluid in the
waste heat pipe 8. By provision of the heat pump unit 2 according
to the present invention, heat can be guided from a lower
temperature position to a higher temperature position. Namely, the
heat Q2' released by the heat pump unit 2 can be larger than the
heat Q2 absorbed from the waste heat pipe 8. By such an
arrangement, the temperature reduced working fluid can be used
again to effectively and fully utilize a large amount of
low-temperature heat source having low enthalpy. This saves the
energy and increases the shaft work W.sub.out of the turbine 11
while enhancing the heat efficiency of the power cycling unit
1.
[0021] In this embodiment, the heat pump unit 2 includes a
compressor 21, a condenser 22, a throttle valve 23, and an
evaporator 24. The compressor 21, the condenser 22, the throttle
valve 23, and the evaporator 24 are connected to each other by
pipes to form a closed circulating system. A second working fluid,
such as a coolant, is filled in the pipes. The compressor 21 is
connected to the turbine 11 of the power cycling unit 1, such that
the shaft work W.sub.out outputted by the turbine 11 drives the
compressor 21, saving the work required for driving the compressor
21 and saving the energy. The compressor 21 compresses the second
working fluid. After compression, the temperature of the second
working fluid is lower than that of the working fluid in the heat
waste pipe 8. Thus, when the second working fluid flows to the
evaporator 24, the second working fluid absorbs the heat Q2 from
the working fluid in the waste heat pipe 8. The throttle valve 23
is used to convert high pressure/low temperature second working
fluid into low pressure/high temperature second working fluid
during an iso-enthalpy process, such that the temperature of the
second working fluid is higher than that of the first working fluid
of the power cycling unit 1. This allows transmission of the heat
Q2' into the second heat exchanger 15 to increase the temperature
of the first working fluid.
[0022] Operation of the power system driven by a low-temperature
heat source of the first embodiment according to the present
invention will now be described with reference to FIG. 2 and
further to FIG. 3 showing a temperature-entropy diagram of the
power cycling unit 1. When the first working fluid flows through
the pump 13, the first working fluid is isentropically compressed,
and the temperature of the first working fluid is increased to
T.sub.o (see a.fwdarw.b in FIG. 3). When the first working fluid
flows through the first heat exchanger 14, the temperature of the
first working fluid is increased from T.sub.0 to T.sub.1 by the
heat Q1 absorbed by the first heat exchanger 14 (see b.fwdarw.c in
FIG. 3). When the first working fluid flows through the second heat
exchanger 15, the temperature of the first working fluid is
increased from T.sub.1 to T.sub.2 by the heat Q2' released by the
heat pump unit 2, heating the first working fluid to an overheated
steam state (see c.fwdarw.d in FIG. 3). Thus, when the first
working fluid having a temperature of T.sub.2 flows through the
turbine 11, the turbine 11 outputs shaft work W.sub.out (see
d.fwdarw.e in FIG. 3). Then, the first working fluid flows to the
condenser 12 to release low-quality waste heat, completing a cycle
(see e.fwdarw.a in FIG. 3).
[0023] The main feature of the power system driven by a
low-temperature heat source according to the present invention is
that the heat of the working fluid in the waste heat pipe 8 can be
absorbed in advance to preheat the first working fluid in the power
cycling unit 1. Since the temperature of the working fluid in the
waste heat pipe 8 drops, the power system driven by a
low-temperature heat source according to the present invention
utilizes the heat pump unit 2 to further absorb heat from the
temperature reduced working fluid in the waste heat pipe 8 and to
covert it into heat with a higher temperature to the second heat
exchanger 15. Thus, the first working fluid can be in an ideal
overheated steam state before entering the turbine 11, increasing
the shaft work W.sub.out of the turbine 11. Furthermore, the shaft
work W.sub.out of the turbine 11 can be used to drive the
compressor 21 of the heat pump unit 2. As a result, in addition to
effective recycling and reuse of the low-temperature heat source
(the working fluid in the waste heat pipe 8), the power system
driven by a low-temperature heat source according to the present
invention can enhance the heat efficiency of the power cycling unit
1 and can effectively save energy.
[0024] With reference to FIG. 4, a power system driven by a
low-temperature heat source of a second embodiment according to the
present invention includes a power cycling unit 1, a heat pump unit
2, and an auxiliary heat pump unit 3. The power cycling unit 1 is
connected to the heat pump unit 2 and the auxiliary heat pump unit
3. The heat pump unit 2 of the second embodiment is substantially
the same as that of the first embodiment and is, therefore, not
described in detail to avoid redundancy.
[0025] In this embodiment, the power cycling unit 1 includes a
turbine 11, a condenser 12, a pump 13, a first heat exchanger 14, a
second heat exchanger 15, and a third heat exchanger 16. The
functions of and connections between turbine 11, the condenser 12,
the pump 13, the first heat exchanger 14, and the second heat
exchanger 15 are substantially the same as those in the first
embodiment and, therefore, not described in detail to avoid
redundancy. In this embodiment, the third heat exchanger 16 is
mounted between the turbine 11 and the second heat exchanger 15 to
absorb heat Q3' released by the auxiliary heat pump unit 3, heating
the first working fluid for the third time.
[0026] The auxiliary heat pump 3 is connected to the third heat
exchanger 16 of the power cycling unit 1 to absorb heat Q3 from the
working fluid in the waste heat pipe 8 and to release the heat Q3'
to the third heat exchanger 16. When the working fluid flows
through an area covered by the first and second heat exchangers 14
and 15, the temperature of the working fluid significantly drops
due to absorption of heat from the working fluid by the first and
second heat exchangers 14 and 15. By provision of the auxiliary
heat pump unit 3 according to the present invention, the heat can
be guided from a lower temperature position to a higher temperature
position. Namely, the heat Q3' released by the auxiliary heat pump
unit 3 can be larger than the heat Q3 absorbed from the waste heat
pipe 8. By such an arrangement, the temperature reduced working
fluid can be effectively used to save the energy and to increase
the shaft work W.sub.out of the turbine 11 while enhancing the heat
efficiency of the power cycling unit 1.
[0027] In this embodiment, the auxiliary heat pump unit 3 includes
a compressor 31, a condenser 32, a throttle valve 33, and an
evaporator 34. The compressor 31, the condenser 32, the throttle
valve 33, and the evaporator 34 are connected to each other by
pipes to form a closed circulating system. A third working fluid,
such as a coolant, is filled in the pipes. The compressor 31 is
connected to the turbine 11 of the power cycling unit 1, such that
the shaft work W.sub.out outputted by the turbine 11 drives the
compressor 31, saving the energy. The compressor 31 compresses the
third working fluid. After compression, the temperature of the
third working fluid is lower than that of the working fluid in the
heat waste pipe 8 that has passed through the first heat exchanger
14 and the heat pump unit 2. Thus, when the third working fluid
flows to the evaporator 34, the third working fluid absorbs the
heat Q3 from the working fluid in the waste heat pipe 8. The
throttle valve 33 is used to convert high pressure/low temperature
third working fluid into low pressure/high temperature third
working fluid during an iso-enthalpy process, such that the
temperature of the third working fluid is higher than that of the
first working fluid entering the third heat exchanger 16 of the
power cycling unit 1. This allows transmission of heat Q3' into the
third heat exchanger 16 to increase the temperature of the first
working fluid for the third time.
[0028] Operation of the power system driven by a low-temperature
heat source of the second embodiment according to the present
invention will now be described with reference to FIG. 4 and
further to FIG. 5 showing a temperature-entropy diagram of the
power cycling unit 1. When the first working fluid flows through
the pump 13, the first working fluid is isentropically compressed,
and the temperature of the first working fluid is increased to
T.sub.0 (see a.fwdarw.b in FIG. 5). When the first working fluid
flows through the first heat exchanger 14, the temperature of the
first working fluid is increased from T.sub.0 to T.sub.1 by the
heat Q1 absorbed by the first heat exchanger 14 (see b.fwdarw.c in
FIG. 5). When the first working fluid flows through the second heat
exchanger 15, the temperature of the first working fluid is
increased from T.sub.1 to T.sub.2 by the heat Q2' released by the
heat pump unit 2, heating the first working fluid to an overheated
steam state (see c.fwdarw.d in FIG. 5). When the first working
fluid flows through the third heat exchanger 16, the temperature of
the first working fluid is increased from T.sub.2 to T.sub.3 by the
heat Q3' released by the auxiliary heat pump unit 3, heating the
first working fluid for the third time (see d.fwdarw.e in FIG. 5).
Thus, when the first working fluid having a temperature of T.sub.3
flows through the turbine 11, the turbine 11 outputs shaft work
W.sub.out (see e.fwdarw.f in FIG. 5). Then, the first working fluid
flows to the condenser 12 to release low-quality waste heat,
completing a cycle (see f.fwdarw.a in FIG. 5).
[0029] In addition to providing the same function and effect of the
first embodiment, the power system driven by a low-temperature heat
source of the second embodiment according to the present invention
provides additional auxiliary heat pump unit(s) 2, 3 corresponding
to the number of additional heat exchanger(s) 15, 16 to effectively
use a large amount of working fluid with low enthalpy and to heat
the first working fluid in the power cycling unit 1 multiple
times.
[0030] In view of the foregoing, the power system driven by a
low-temperature heat source according to the present invention
includes at least two heat exchangers in which the first heat
exchanger 14 is used to initially heat the first working fluid, and
subsequent heat exchanger(s) 15, 16 cooperate with corresponding
heat pump unit(s) 2, 3 to further effectively use the temperature
reduced working fluid in the waste heat pipe 8. Thus, a large
amount of working fluid with low enthalpy can be effectively used
while saving energy.
[0031] Thus since the invention disclosed herein may be embodied in
other specific forms without departing from the spirit or general
characteristics thereof, some of which forms have been indicated,
the embodiments described herein are to be considered in all
respects illustrative and not restrictive. The scope of the
invention is to be indicated by the appended claims, rather than by
the foregoing description, and all changes which come within the
meaning and range of equivalency of the claims are intended to be
embraced therein.
* * * * *